被災下水処理場の暫定処理水に対する塩素やオゾン，紫外線による消毒方法の評価に関する研究

京都大学0048新制・課程博士博士(工学)甲第22765号工博第4764号新制||工||1745(附属図書館)京都大学大学院工学研究科都市環境工学専攻(主査)教授 田中 宏明, 教授 高岡 昌輝, 准教授 西村 文武学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA

An Energy-Efficient Secure Scheme in Wireless Sensor Networks

We propose an energy-efficient security scheme in wireless sensor networks. The proposed scheme converts sensing data using TinyMD5, which is a variation of MD5, a one-way hash function, and can solve the collision problem of hash value that occurs when MD5 is modified. In addition, it strengthens security capabilities by transmitting data through multiple paths after conversion with TinyMD5 and divides the data to make decryption of the original data difficult. To show the superiority of the proposed algorithm, we compare it with the existing schemes through simulations. The performance evaluation results show that the proposed scheme maintains security better than the existing scheme, improving the communication cost and the network lifetime

Difficulty-Focused Contrastive Learning for Knowledge Tracing with a Large Language Model-Based Difficulty Prediction

This paper presents novel techniques for enhancing the performance of knowledge tracing (KT) models by focusing on the crucial factor of question and concept difficulty level. Despite the acknowledged significance of difficulty, previous KT research has yet to exploit its potential for model optimization and has struggled to predict difficulty from unseen data. To address these problems, we propose a difficulty-centered contrastive learning method for KT models and a Large Language Model (LLM)-based framework for difficulty prediction. These innovative methods seek to improve the performance of KT models and provide accurate difficulty estimates for unseen data. Our ablation study demonstrates the efficacy of these techniques by demonstrating enhanced KT model performance. Nonetheless, the complex relationship between language and difficulty merits further investigation.Comment: 10 pages, 4 figures, 2 table

Towards accurate accounting of cellular data for TCP retransmission

The current architecture supporting data services to mobile devices is built below the network layer (IP) and users receive the payload at the application layer. Between them is the transport layer that can cause data consumption inflation due to the retransmission mecha-nism that provides reliable delivery. In this paper, we examine the accounting policies of five large cellular ISPs in the U.S. and South Korea. We look at their policies regarding the transport layer re-liability mechanism with TCP’s retransmission and show that the current implementation of accounting policies either fails to meet the billing fairness or is vulnerable to charge evasions. Three of the ISPs surveyed charge for all IP packets regardless of retransmis-sion, allowing attackers to inflate a victim’s bill by intentionally re-transmitting packets. The other two ISPs deduct the retransmitted amount from the user’s bill thus allowing tunneling through TCP retransmissions. We show that a “free-riding ” attack is viable with these ISPs and discuss some of the mitigation techniques

Potential-Based Fracture Mechanics Using Cohesive Zone and Virtual Internal Bond Modeling

233 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.The characterization of nonlinear constitutive relationships along fracture surfaces is a fundamental issue in mixed-mode cohesive fracture simulations. A generalized potential-based constitutive theory of mixed-mode fracture is proposed in conjunction with physical quantities such as fracture energy, cohesive strength and shape of cohesive interactions. The potential-based model is verified and validated by investigating quasi-static fracture, dynamic fracture, branching and fragmentation. For quasi-static fracture problems, intrinsic cohesive surface element approaches are utilized to investigate microstructural particle/debonding process within a multiscale approach. Macroscopic constitutive relationship of materials with microstructure is estimated by means of an integrated approach involving micromechanics and the computational model. For dynamic fracture, branching and fragmentation problems, extrinsic cohesive surface element approaches are employed, which allow adaptive insertion of cohesive surface elements whenever and wherever they are needed. Nodal perturbation and edge-swap operators are used to reduce mesh bias and to improve crack path geometry represented by a finite element mesh. Adaptive mesh refinement and coarsening schemes are systematically developed in conjunction with edge-split and vertex-removal operators to reduce computational cost. Computational results demonstrate that the potential-based constitutive model with such adaptive operators leads to an effective and efficient computational framework to simulate physical phenomena associated with fracture. In addition, the virtual internal bond model is utilized for the investigation of quasi-brittle material fracture behavior. All the computational models have been developed in conjunction with verification and/or validation procedures.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Potential-Based Fracture Mechanics Using Cohesive Zone and Virtual Internal Bond Modeling

233 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.The characterization of nonlinear constitutive relationships along fracture surfaces is a fundamental issue in mixed-mode cohesive fracture simulations. A generalized potential-based constitutive theory of mixed-mode fracture is proposed in conjunction with physical quantities such as fracture energy, cohesive strength and shape of cohesive interactions. The potential-based model is verified and validated by investigating quasi-static fracture, dynamic fracture, branching and fragmentation. For quasi-static fracture problems, intrinsic cohesive surface element approaches are utilized to investigate microstructural particle/debonding process within a multiscale approach. Macroscopic constitutive relationship of materials with microstructure is estimated by means of an integrated approach involving micromechanics and the computational model. For dynamic fracture, branching and fragmentation problems, extrinsic cohesive surface element approaches are employed, which allow adaptive insertion of cohesive surface elements whenever and wherever they are needed. Nodal perturbation and edge-swap operators are used to reduce mesh bias and to improve crack path geometry represented by a finite element mesh. Adaptive mesh refinement and coarsening schemes are systematically developed in conjunction with edge-split and vertex-removal operators to reduce computational cost. Computational results demonstrate that the potential-based constitutive model with such adaptive operators leads to an effective and efficient computational framework to simulate physical phenomena associated with fracture. In addition, the virtual internal bond model is utilized for the investigation of quasi-brittle material fracture behavior. All the computational models have been developed in conjunction with verification and/or validation procedures.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Punching Shear Behavior of Two-Way Concrete Slabs Reinforced with Glass-Fiber-Reinforced Polymer (GFRP) Bars

This study investigated the punching shear behavior of full-scale, two-way concrete slabs reinforced with glass fiber reinforced polymer (GFRP) bars, which are known as noncorrosive reinforcement. The relatively low modulus of elasticity of GFRP bars affects the large deflection of flexural members, however, applying these to two-way concrete slabs can compensate the weakness of the flexural stiffness due to an arching action with supporting girders. The test results demonstrated that the two-way concrete slabs with GFRP bars satisfied the allowable deflection and crack width under the service load specified by the design specification even in the state of the minimum reinforcement ratio. Previous predicting equations and design equations largely overestimated the measured punching shear strength when the slab was supported by reinforced concrete (RC) girders. The strength difference can be explained by the fact that the flexural behavior of the supporting RC beam girders reduces the punching shear strength because of the additional deflection of RC beam girders. Therefore, for more realistic estimations of the punching shear strength of two-way concrete slabs with GFRP bars, the boundary conditions of the concrete slabs should be carefully considered. This is because the stiffness degradation of supporting RC beam girders may influence the punching shear strength